I do an uprated ignition module that is 'racing'. I've had great results with it. it does make a real difference, admittedly the rest of the motor on my 400 is tuned (and was therefore "ready" for this).
if you want to tune yours have a look at fitting the 2003-8 cam called the '08' cam. it loses about 3 yards off the corner and gets it back through 4, 5 and 6th gears.